The mainstay of osteoporosis treatment remains anti-resorptive approach by way of bisphosphonates. Bisphosphonate treatment prevents further bone loss but is ineffective for making up lost bone. Bone forming (osteogenic/anabolic) therapy, which is the ultimate goal for osteoporosis treatment, is limited only to parathyroid hormone (PTH). In addition to being extremely costly, PTH is not readily available in India. Lately, reports of development of osteosarcoma as a result of prolonged use of PTH have been reported. Therefore, finding new bone anabolic agent, that is safe and could increase bone mass and strength and thereby reducing the risk of osteoporotic fracture is an unmet medical need.
Epidemiological as well as in vitro studies suggest that consumption of flavonoids is beneficial for bone health. Majority of the studies on the effects of flavonoids in bone involve isoflavones. Isoflavones such as genistein and diadzein are phytoestrogens with strong anti-osteoclastogenic actions. Isoflavone-rich soy food has been tested in clinical trials with mixed results (Horcajada et al 2000, Ma D F et al 2008). Kaempferol was reported as phytoestrogen and can be used as therapeutic agent for osteoblasts (PCT publication no. WO 2005/077358 A1 dated 25 Aug. 2005). A composition comprising gum Arabic with acacia derivatives has also been used for the conditions of osteoporosis, which has been reported to promote calcium absorption (PCT/EP 2008/006462). Comparative bioavailability of different flavonols has been reported after administration of three different preparations i.e capsules, drops and tablets of gingko biloba, of which, drops have shown higher absorption. Kaempferol (K) is structurally similar to quercetin and contributes about 25-33% of mean total flavonol intake in human, which estimates at 6-10 mg per day in the USA and the Netherlands.
Kaempferol is reported to have anti-oxidant, anti-viral, anti-bacterial, cardio-protecting (prevent atherosclerotic plaque formation) and chemo-preventive properties. It is a non-steroidal phytoestrogen that acts like hormone estrogen. More recently their activity in breast cancer and as anti-osteoporosis, mediated via estrogen receptor, is an active area of research.
It has been reported that gum Arabic and acacia derivatives has tendency to promote calcium absorption when given orally (PCT/EP 2008/006462). Gingko biloba extract after administration of three different preparations in the form of capsules, drops and tablets, it has been observed that drops have shown higher absopriton (Wojcicki J, Gawronska-Szklarz, B, Bieganowski, W Patalan, M, Smulski, H K, Samochowiec, L, Zakrzewski, J. Mater. Med. Pol. (1995) 27(4) 141-146. Kaempferol (K) is structurally similar to quercetin and contributes about 25-33% of mean total flavonol intake in human, which estimates at 6-10 mg per day in the USA and the Netherlands [Hertog M G, Hollman P C, Katan M B, Kromhout D., Nutr. Cancer. 1993, 20:21-29; Sampson L, Rimm E, Hollman P C, De Vries J H, Katan M B., J. Am. Diet Assoc. 2002, 102:1414-1420]. The use of biodegradable nano-matrix formulations by layer-by-layer (LbL) adsorption technique represents an alternative to other colloidal carriers viz: liposomes, niosomes, bilosomes, aquasomes, nanoparticles and microparticles as well as for delivering the large quantities of water soluble as well as water insoluble (hydrophilic/hydrophobic) drugs for controlled delivery and better targeting efficacy [Bentina, 1996; Allen and Cullis, 2004; Brigger et al., 2002; Totchilin, 2005 Bentina, S. (Ed.) 1996; Microencapsulation, Drugs and the Pharmaceutical Science. Marecl Dekker, New York; Allen, T. M., Cullis, P. R., 2004; Drug Delivery systems: entering the mainstream. Science 303, 1818-1822; Brigger, I., Dubernet, C., Couvreur, P., 2002; Nanoparticles in cancer therapy and diagnosis. Adv. Drug Deliv. Rev. 54, 631-651; Totchilin, V. P., 2005; Recent advances with liposome as pharmaceutical carriers, Nat. rev. Drug Discov. 4, 145-160]. Though all these mentioned techniques/technologies fulfill the optimal delivery of drugs with improved performance within the specified cell or tissue however, these technologies have come to an age and altogether transformed into mature discipline. The excipient used in the proposed systems are generally regarded as safe (GRAS) and is preferably approved by the USFDA.
Recently developed, porous microparticles (MP) of inorganic origin have a great potential to allocate the drug in their nanopores (nanoreservoir) and having features of biological stability with sustained release property. Most of researchers have reported use of porous architecture for fabrication of assembly viz. porous hollow silica nanoparticles [Li, Z. Z., Wen, L. X., Shao, L., Chen, J. F. Fabrication of porous hollow silica nanoparticles and their applications in controlled drug release. [J. Control Rel. 2004, 98, 245-254], porous hydroxyapatite [Kim, H. W., Knowles, J. C., Kim, H. E., Hydroxyapatite/poly (ε-caprolactone) composite coatings on hydroxyapatite porous bone scaffold for drug delivery. Biomaterials 2004, 25, 1279-1287], porous calcium carbonate microparticles [Volodkin, D. V., Larionova, N. I., Sukhorukov, G. B.,. Protein encapsulation via porous CaCO3 microparticles templating. Biomacromolecules 2004, 5, 962-972; Volodkin, D. V., Petrov, A. I., Prevt, M., Sukhorukov, G. B., Matrix polylelectrolyte microcapsules: new system for macromolecule encapsulation. Langmuir 2004, 20, 3398-3406] and other porous architecture. The novel approach in this regard is the development of smart, functional, organized system by LBL self-assembling technique for the micro-encapsulation of bioactives [Caruso, F., Nano engineering of particle surface Adv. Mater. 2001, 13, 11-22; Peyratout, C. S., Dahne, L., Tailor-made polyelectrolyte microcapsules: from multilayers to smart containers. Angew. Chem. Int. ed. 2004, 434, 3762-3783; Decher, G., Schlenoff, J. B. (Eds.), 2003. Multilayer Thin films: Sequential Assembly of Nanocomposite Material. Wiley-VHC, Weinheim].
Among the decomposable core, porous CaCO3 MP elicits interest due to its wide industrial, technological and drug delivery applications [Caruso F., Caruso R. A, Mohwald H., Nanoenginnering of inorganic and hybrid hollow spheres by colloidal templating, Science, 1998, 282, 1111-1114; Ye S., Wang C., Liu X., Tong Z., Deposition temperature effect on release rate of indomethacin microcrystals from microcapsules of layer-by-layer assembled chitosan and alginate multilayer films, J. Control. Release, 2005, 106, 319-328; Donath E., Moya S., Neu B., Sukhorukov G. B., Georgieva R., Voigt A., Baumler H., Kiesewetter H., Mohwald H., Hollow polymer shells from biological templates: fabrication and potential applications, Chem. Eur. J., 2002, 8, 5481-5485; An, Z. H., Lu G., Mohwald H., Li J. B., Self assembly of human serum albumin and L-alpha-dimyristoylphosphatidic acid (DMPA) microcapsules for controlled drug release, Chem. Eur. J., 2004, 10 5848-5852]. The powder XRD data reveals (illustrated in FIG. 1A) that all polymorphic forms of the CaCO3 have been obtained during fabrication of porous particles viz: calcite (rhombohedral), aragonite (hexagonal) and vaterite (spherical) due to mutual transformation between them (Volodkin, D. V., Larionova, N. I., Sukhorukov, G. B., Protein encapsulation via porous CaCO3 microparticles templating. Biomacromolecules 2004, 5, 962-972) using conventional method of co-precipitation of calcium chloride dihydrate and sodium carbonate. Lactalbumin was encapsulated by means of the proposed technique yielding a content of 0.6 pg protein per microcapsule. Horseradish peroxidase saves 37% of activity after encapsulation. However, the thermostability of the enzyme was improved by encapsulation. The results demonstrate that porous CaCO3 microparticles can be applied as microtemplates for encapsulation of proteins into polyelectrolyte capsules at neutral pH as an optimal medium for a variety of bioactive material, which can also be encapsulated by the proposed method. Volodkin et al., 2004b proposed a new approach to fabricate polyelectrolyte microcapsules is based on exploiting porous inorganic microparticles of calcium carbonate. The structural investigations on multilayer composed of strong flexible PE's revealed that enzymes can be incorporated in multilayer for either biosensing or multistep biocatalysts. [Decher et al., Curr Opin Coll Interface Sci 3: 32-9 1998]. Volodkin et al., [Langmuir, 2: 3398-3406 (2004a)], used porous microparticles of calcium carbonate for encapsulation of protein in polymer-filled microcapsules by means of electrostatic layer-by-layer assembly. Porous inorganic microparticles of calcium carbonate has been proposed as new approach to fabricate polyelectrolyte microcapsules [Volodkin et al., Langmuir, 2: 3398-3406 2004b]. Caruso [Adv. Mater. 13, 11-22 2001]; reviewed the creation of core-shell particles and its application as building blocks for photonic crystals, in multi-enzyme biocatalysts, and in drug delivery. A novel encapsulation method for ibuprofen (IBU) on porous CaCO3 MP doped with polystyrene sulfonate (PSS) by combination of methods using LbL assembly has been studied by [Wang et al., Journal of material chemistry, 2007]. Schlenoff et. al. 2001, studied the growth of multilayers made from a combination of a weak polyacid and a strongly dissociated polycation as a function of salt concentration and molecular weight. Gao et al., [Langmuir, 7: 3491-3495 (2001)] developed a drug delivery system based on spontaneous deposition of soluble, low molecular weight therapeutic agents for the purpose of sustaining drug release. LbL assembly of oppositively charged PE's onto melamine formaldehyde colloidal particles, followed by core removal at low pH has yielded intact hollow microcapsules. Gupta et al., 2008, has successfully allocated paclitaxel (PTX). in their nanopores (nanoreservoir) and reported biological stability along with sustained release properties. Bhadra et al., 2004, successfully carried out comparative study on development and characterization of the multicomposite architecture using calcium phosphate and RBC as core particles for LbL assembly. The elasticity of the capsules can be made to vary within 0.05-10 GPa, depending on the composition, treatment and filling of the capsule [Fery and Vinogradova, New J. Phys. 6, 1-13, 2004]. Studies from our laboratory have revealed that Kaempferol exerts bone sparing action in OVx rats by stimulating bone formation. Kaempferol treatment to OVx rats resulted in the increase in osteoprogenitor cells as well as inhibition of adipocyte differentiation from bone marrow cells compared with the OVx group treated with vehicle. In addition, Kaempferol has no estrogen agonistic effect at the uterine level. Thus, Kaempferol has therapeutic promise for postmenopausal bone loss. However, one of the major challenges in developing Kaempferol as therapeutics for osteoporosis is their rapid elimination from the body after oral administration and poor oral bioavailability (Scalbert et al, Crit. Rev Food Sci. Nutr. 45(4) 287-306 (2005)]; Trivedi et al, Mol. Cell. Endo. 289; 85-93 (2008)]. It has been observed that Kaempferol undergo post-absorption sharp elimination phase which eventually go below detection limit after 6 hr. However, there exists a distinct scope for improvement in the case of Kaempferol for therapeutic use, by increasing its bioavailability. Better bioavailability would enhance anti-osteoporotic effects of Kaempferol as well as reduce its dose (indicating better safety).